It's an old topic, but I'll add one here I will never forget... I was at a (local) convention in Portland, OR and one of the 'celebrities' who were signing was Herbert Jefferson Jr. (Boomer from Classic BSG) and there was a severely handicapped young man who really wanted his autograph, but he was charging $20 for it (okay, that part is fine... but it gets worse)....
The Handicapped person was in a full on mobil transport where he had to be more or less leaned back in, so it was more than a wheel chair, but with much effort, he was able to get his wallet out to get some money... he only had about $12...
Instead of Jefferson being a decent man and taking the $12 for the guy who obviously was a big fan (of his character at least), and giving the young man an autograph and making him happy, he decided to 'help' the young man by taking his wallet and looking through it for additional money... after a failed attempt, he told the young man "sorry, you don't have enough' and instructed him to find more....
Had he done "the right thing" and given the autograph, hell, I would have offered up the $8 to pay him, but after seeing that display first hand, not only did I instantly dislike him, but refused to have him sign a photo for me....
That, my friends, is a first class jerk...